In vitro studies of two closely related biological functions are proposed. One is to study the mechanism of generalized recombination using newly constructed transformable E. coli strains which carry colicin El-trp plasmid. Following in vivo studies to determine the basic conditions for recombination, attempts will be made to reconstruct whole recombination processes in vitro. The other in vitro studies will deal with the prophage induction processes in vitro. The other in vitro studies will deal with the prophage induction process following ultraviolet light irradiation. By employing the biochemical assay procedure which we have recently developed, basic cellular functions related to the induction process will be characterized. We will attempt to establish a total in vitro prophage induction system. BIBLIOGRAPHIC REFERENCES: Oishi, M., S.D. Cosloy and S.K. Basu (1975). Transformation-mediated Recombination in Escherichia coli. Mechanisms in Recombination, edited by R.R. Grell, p 145-154. Basu, S.K. and M. Oishi (1975). Factor which affects the mode of genetic recombination in E. coli. Nature, 253:138-140.